A large number of alarm systems are presently manufactured to provide protection against various problem situations which may be experienced in a residence, an office building, manufacturing facility, or any other premises. Fire, burglary, panic or other unique alarm situations can be sensed locally and the information can then be transmitted by a local communicator through appropriate connections to the local telephone lines for transmission to a receiver location at a suitable central location. In this manner, the information can in turn be relayed to the appropriate agency, such as a fire department, a police department, or other desired recipient.
In a typical alarm system, such as a burglar alarm system, the system is connected via telephone lines to an alarm monitoring station. For example, the premises typically may have a protective circuit which may comprise a number of intrusion detectors, a voltage source, a sensing relay and wiring connecting these components together The alarm system generally includes an alarm control panel where the sensing relay may be located, a key-operated switch, and a latching relay. When an alarm condition occurs, the latching relay is caused to activate an audible/or visible warning device or a signal that is transmitted via telephone lines to a police station or central office. In some instances, a dedicated telephone line from the premises to the police station is used. Alternatively, a shared telephone line may be used and a particular signal is issued on the telephone line corresponding to the alarm condition that has occurred
Conventional network telephone systems utilized in such an alarm system typically require transmission lines or cables from a local telephone company's central office to individual fixed locations, such as the home or office building. The telephone trunk lines entering the fixed location are connected to one or more individual telephone sets or to a switching unit that may be coupled to a PBX or other type of internal office system network.
In a telephone network system, when an alarm system is tripped at the protected premises, the telephone line is seized and loop current is produced. The telephone network's central office issues a dial-tone to the alarm system which upon recognition by the premises terminal dialer, the central monitoring receiver telephone number is automatically dialed. The central office of the telephone company then decodes the telephone number and a ring signal is sent to the alarm system central monitoring receiver. The central monitoring receiver responds by going "off-hook" and sends a handshake signal to the protected premises. The receiver at the protected premises responds to the handshake signal by sending data to the central receiver. If the data is sent and received correctly, the central monitoring receiver sends a "kiss-off" signal to the protected premises terminal, and the protected premises terminal responds to the "kiss-off" signal by returning an "on-hook" condition. At this point, the communication is completed until a new alarm is actuated.
From the above sequence of events, it is clear that the essential link between the protected premises and the alarm monitoring station or central office is the telephone line; however this link is also the weakest in the alarm system. The telephone line may be inadvertently cut such as by construction equipment, or deliberately cut by an intruder prior to his unlawful entry into the protected premises, such that no information would thereafter be transmitted to the central alarm monitoring station. Loss of this connection to the telephone exchange results in a loss of dial tone availability and loss of access to the central telephone network and alarm monitoring station. Even if the telephone line is intact, transmission failures may effect the operation of a telephone network land-line based alarm system. For example, a busy signal may appear on the telephone line resulting in loss of access to the central office and alarm-monitoring station. Additionally, inaccurate data transmission causing the receiver to reject the transmission, may result when the system goes "on-hook" at either the central office or at the alarm monitoring station without sending either a handshake signal, an acknowledge signal or a "kiss-off"
Therefore, although the telephone land-line based alarm system is generally satisfactory for providing communication between the protected premises and an alarm-monitoring station, a potential problem does exist with such systems. In an attempt to improve such systems, telephone systems utilizing cellular mobile radio telephones have been used in alarm systems. Cellular- type radio/telephone communication systems provide a wireless communication path between the protected premises and the central office of the telephone network, thereby minimizing several of the problems associated with telephone lines. Such a wireless alarm system is described in U.S. Pat. No. 4,577,182, issued to James W. Millsap et al. on Mar. 18, 1986 and entitled "Alarm System". However, existing cellular-type radio/telephone communication systems require complex programming of the cellular transceiver to dial telephone numbers of the alarm monitoring station. These systems require complex communicators with their associated high costs and reliability problems which effect the overall integrity of the alarm system.
A need has thus arisen for an efficient, cost-effective and reliable cellular-type radio/telephone communication system included within an alarm system to provide wireless communication. Additionally, in order to enhance the desirable features of conventional telephone network based systems utilizing land lines in alarm systems, a need has arisen for a system in which a redundant, backup communication path exists in the form of a wireless communication path.